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Simplify coding style of is_valid_ascii()

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Calculate end of input rather than maintaining length,
per prior suggestion from Heikki Linnakangas. In passing,
use more natural language in a comment.

Discussion: https://www.postgresql.org/message-id/b4648cc2-5e9c-c93a-52cc-51e5c658a4f6%40iki.fi
This commit is contained in:
John Naylor
2022-08-05 13:07:31 +07:00
parent 82593b9a3d
commit 6b41a1579b
1 changed files with 3 additions and 3 deletions
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6
src/include/mb/pg_wchar.h
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@ -709,13 +709,14 @@ extern WCHAR *pgwin32_message_to_UTF16(const char *str, int len, int *utf16len);
static inline bool static inline bool
is_valid_ascii(const unsigned char *s, int len) is_valid_ascii(const unsigned char *s, int len)
{ {
const unsigned char *const s_end = s + len;
uint64 chunk, uint64 chunk,
highbit_cum = UINT64CONST(0), highbit_cum = UINT64CONST(0),
zero_cum = UINT64CONST(0x8080808080808080); zero_cum = UINT64CONST(0x8080808080808080);
Assert(len % sizeof(chunk) == 0); Assert(len % sizeof(chunk) == 0);
while (len > 0) while (s < s_end)
{ {
memcpy(&chunk, s, sizeof(chunk)); memcpy(&chunk, s, sizeof(chunk));
@ -734,11 +735,10 @@ is_valid_ascii(const unsigned char *s, int len)
*/ */
zero_cum &= (chunk + UINT64CONST(0x7f7f7f7f7f7f7f7f)); zero_cum &= (chunk + UINT64CONST(0x7f7f7f7f7f7f7f7f));
/* Capture any set bits in this chunk. */ /* Capture all set bits in this chunk. */
highbit_cum |= chunk; highbit_cum |= chunk;
s += sizeof(chunk); s += sizeof(chunk);
len -= sizeof(chunk);
} }
/* Check if any high bits in the high bit accumulator got set. */ /* Check if any high bits in the high bit accumulator got set. */